Staining | EPFL Graph Search

Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissues), in cytology (microscopic study of cells), and in the medical fields of histopathology, hematology, and cytopathology that focus on the study and diagnoses of diseases at the microscopic level. Stains may be used to define biological tissues (highlighting, for example, muscle fibers or connective tissue), cell populations (classifying different blood cells), or organelles within individual cells. In biochemistry, it involves adding a class-specific (DNA, proteins, lipids, carbohydrates) dye to a substrate to qualify or quantify the presence of a specific compound. Staining and fluorescent tagging can serve similar purposes. Biological staining is also used to mark cells in flow cytometry, and to flag proteins or nucleic acids in gel electrophoresis. Light microscopes are used for viewing stained sa

Hormonal regulation of Stat5 in the mammary gland - from signaling to morphogenesis

Sergio Klinke

The mammary gland development is regulated by steroid and peptide hormones and occurs mainly after birth, compared to the majority of the other organs in the body. The principal hormones responsible for the breast development are the estrogen, the progesterone, the growth hormone, the epidermal growth factor and the prolactin. The latter one is of specific interest since it is required for further development of the gland through pregnancy and lactation. During pregnancy and lactation, alveolar structures develop and differentiate into secretory cells. The signal transducer and activator of transcription 5 (Stat5) is known to be the main effector of prolactin signaling during pregnancy, inducing alveologenesis and differentiation of epithelial cells into secretory cells. I investigated if Stat5 has a role before pregnancy. Protein expression as well as mRNA expression analysis of glands from ovariectomized mice which were artificially stimulated with ovarian hormones (estrogen and progesterone) and control vehicle showed evidences that Stat5 expression can be stimulated by these two hormones. Contrary to the role established until now for stat5 in the mammary gland, I found by fluorescence visualization of Stat5-null epithelium as well as whole mount staining of the same glands that Stat5 is required even before pregnancy since null epithelium showed highly reduced growth already in 3 weeks-old virgin mice. This may indicate a new role for this protein in cell proliferation or survival in early stages of mouse mammary development. Furthermore, transplantation experiment of Stat5-null epithelium into wild-type recipient mice showed that pregnancy state was not able to rescue the normal phenotype. This may be due to complete loss of these cells which happened during the 5 weeks left for the transplanted epithelium to expand the cleared fat pad. This discovery opens a new debate on Stat5 role in the mammary gland development.

2008

Dual-Activatable Cell Tracker for Controlled and Prolonged Single-Cell Labeling

Salome Riccarda Püntener, Pablo Rivera Fuentes

Cell trackers are fluorescent chemical tools that facilitate imaging and tracking cells within live organisms. Despite their versatility, these dyes lack specificity, tend to leak outside of the cell, and stain neighboring cells. Here, we report a dual-activatable cell tracker for increased spatial and temporal staining control, especially for single-cell tracking. This probe overcomes the typical problems of current cell trackers: off-target staining, high background signal, and leakage from the intracellular medium. Staining with this dye is not cytotoxic, and it can be used in sensitive primary cells. Moreover, this dye is resistant to harsh fixation and permeabilization conditions and allows for multi-wavelength studies with confocal microscopy and fluorescence-activated cell sorting. Using this cell tracker, we performed in vivo homing experiments in mice with primary splenocytes and tracked a single cell in a heterogeneous, multicellular culture environment for over 20 h. These experiments, in addition to comparative proliferation studies with other cell trackers, demonstrated that the signal from this dye is retained in cells for over 72 h after photoactivation. We envision that this type of probes will facilitate the analysis of single-cell behavior and migration in cell culture and in vivo experiments.

AMER CHEMICAL SOC2020

Design and Synthesis of Gatekeeper Coated Dendritic Silica/Titania Mesoporous Nanoparticles with Sustained and Controlled Drug Release Properties for Targeted Synergetic Chemo-Sonodynamic Therapy

Samira Malekmohammadi, Saba Rezakhani

New dendritic silica/titania mesoporous nanoparticles (DSTNs) loaded with curcumin (CUR) were synthesized and coated with polyethylenimine-folic acid groups (PEI-FA) for an ultrasound (US)-triggered drug release and combined chemo-sonodynamic therapy. The PEI-FA groups play a gatekeeper role, strongly encapsulate the CUR molecules inside the nanocarrier, and prevent the unwanted premature release by blocking the mesoporous channels. The results showed that the specific cancer cell uptake is improved by FA groups on the surfaces of DSTNs via receptor-mediated endocytosis. The TiO2 layer as a sonosensitizer agent coated on the mesoporous silica nanoparticles generates reactive oxygen species. Following the US irradiation, the PEI molecules were cut off by free radicals, including OH center dot and O-2(-), on the exterior surface of DSTNs, and the CUR loaded in the nanocarrier was then released into the cancer cell cytosol. The release profiles of the CUR@PEI-FA-DSTN system showed that the amount of CUR released from DSTNs is controlled by tuning the US radiation time. The results of the MTT cytotoxicity tests of free CUR, free PEI-FADSTN nanocarrier, and CUR@PEI-FA-DSTNs against A549 (human lung carcinoma cell lines) and HeLa (human cervical carcinoma cell lines ( showed that the toxicity of CUR@PEI-FA-DSTNs is higher than those of CUR and PEI-FA-DSTNs alone. In addition, the specific targeting ability, the cellular uptake, and the anticancer activity of the synthesized compounds for targeted cancer treatment were investigated using different staining methods and fluorescence microscopy. The results revealed that the new system, CUR@PEI-FA-DSTNs, can be considered as a potent drug delivery system for increasing effectiveness of the anticancer activity of curcumin in the combined chemo-sonodynamic therapy.

2019